Well getting pregnant at teen age to me has a lot to do with self esteem.
You have to be confident about yourself that way that you're worth to be loved without being extrasomething... if it's extra smart, extra stupid, extra talented, extra beautiful (and we're usually only talking about outside beauty here)... you have to be loved just for who you are. Many parents fail to give that feeling and that confidence to their children.
Whatever the reasons are... many parents do not really have a fair chance to give that to their children cuz they have to work in three jobs nowadays. Many parents are missing exactly that self esteem also.
Many parents still are not able to teach their children the simple way of how to protect themselves from becoming parents if they do not want.
You'll just not give yourself away too easy if you're able to feel self esteem and self confidence and know you're worth to be loved and have faith in yourself and life. To protect yourself from getting pregnant if you do not want even when you decide to have sex is nothing you have to be extra intelligent for. It's just an expression of how to deal with responsiblity for your very own self. That way at least you can still direct your own life a bit.
There's nothing wrong with waiting till you're really ready and having faith in that who really loves you will wait also.
It's still about adults in this world being authentic role models. How they deal with responsibility towards themselves and towards others. How they do love etc.
Many kids do lose faith in their parents early these days. Lots of reasons.
That's probably also what happened in the Spears family... if you can still talk of one. Well I'm carefull with my judgement in this case as I'm fed only by media and do watch the rest only from very far.
However I guess Jamie L. probably thought if she wants a family, she has to start her own better. Hope that's not too much to her, cuz she is pretty young and it was already too much for her older sister before.
Still there are young ladies in her situation who do get their lifes and that of their babies on track pretty well.